1 3 8 2 .] Recent Literature. 3 1 7 



praeoral lobe of many Invertebrate forms, and the primitive posi- 

 tion of the Vertebrate mouth on the ventral side of the head 

 affords a distinct support for this view." • 



Gegenbaur's theory that the pairs of cranial nerves represent so 

 many segments, and his segmental theory of the skull, which has 

 replaced the old-fashioned vertebrate theory of the skull, is appa- 

 rently endorsed by Balfour, who states that " the posterior part of 

 the head must have been originally composed of a series of so- 

 mites like those of the trunk, but in existing Vertebrates all trace 

 of these, except in so far as they are indicated by the visceral 

 clefts, has vanished in the adult. The cranial nerves, however, 

 especially in the embryo, still indicate the number of anterior so- 

 mites," etc. 



Part 1 is concluded by a chapter on the mode of origin and 

 homologies of the germinal layers of animals in general, and with 

 a discussion of larval forms. 



Part 11, or the second half of the book is devoted to Organo- 

 geny, or the mode of origin of the different organs of the verte- 

 brate body, and this important part is characterized by the same 

 full, critical treatment as in the first part, with consideration of 

 the theoretical bearings of facts, such as seem at least in the main 

 warranted by our present knowledge of the facts. 



The work is a most stimulating one, and will greatly advance 

 in English-speaking countries the study of what is the most diffi- 

 cult field of research in biology. 



Elliott's Seal Islands of Alaska. 1 — This entertaining and 

 unusually well illustrated monograph of the fur-seal, hair-seal, 

 sea-lion, and walrus is exceptionally well done. The story is 

 really a fascinating one, and the author's sketches of these ani- 

 mals in various ages and altitudes are apparently by far the best 

 that have ever been executed. A number of important hitherto 

 doubtful points have been cleared up by Mr. Elliott, especially 

 those relating to the breeding habits of these creatures. The re- 

 port, while of particular economic value, is also one of the most 

 important works on natural history which has been published by 

 our Government, containing as it does the results of several years 

 of arduous study and close observations on the bleak, out-of-the- 

 way Prybilov group of islands. 



Although the seal is not a fish, the volume not inappropriately 

 appears as a special Bulletin under the direction of the Com- 

 missioner of Fish and Fisheries. 



1 U. S. Commission of Fish and Fisheries Spencer F. Baud, Commissioner. 176. 

 Speei.il IJ:,|]etiii. AM-. ,,f Alaska. By Henry W. 



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